Rad Flush - antifreeze question

So back from the shop, C$124 poorer.

They said there was air trapped in the coolant system. I asked how they got it out and it was a vague "using our special equipment" and "uncapping and letting it run for 45 minutes." Tried to get more information on said "special equipment" out of them but don't think the desk guy knew specifically what they did.

That bill also includes a tire rotation and clearly overcharging me for coolant. I hate taking it in! But oh well, the price I pay for peace of mind.

In other news, the accelerator pump on the carb is not working properly (likely cause of the stall and rough acceleration). And the master cyclinder is leaking. I really want to repair it all myself before I sell it but no time unfortunately (they wanted $300 for the master cyclinder alone). Off on a year long backpacking trip through south america next week! Family will sell the van while I am gone.

Thanks for all your advice and help on this guys. I'm going to miss doing this!

I know you are focused on trapped air in the system causing the problem and it may be, but on a 1978 van if the radiator is original I would suspect that the radiator flush may have dislodged some stuff causing a blockage in your cooling tubes. You said it ran fine before the flush the only other thing you changed was the thermostat. I have had brand new ones not open all the way. I would put both in a pan of water and bring it to boiling the T stat should open about 1/4 in. Make sure the T stat is installed spring side down I made that mistake once. You can check your radiator with an IR gun and take readings in a grid pattern from top to bottom if you see cold spots that would indicate a blockage. You should read a change in temp from top to bottom of about 50 degrees in a functioning radiator. Also you can shoot the thermostat housing and the sensor in your head that sends the reading to your dash gauge and compare these readings to your IR gun readings. These sensors do fail and gauges can be inaccurate. I would do these simple tests first before you take it in.

Mopar Accurate Gauge is an Oxymoron.

Probably the most overlooked and most priceless test that can be given a cooling system is an extended pressure test to full rated pressure.

And musn't overlook COLD leaks in diesel equipment.

Another alternative is to just pull the thermostat. The engine will run without one installed. I've had my hands on a few of these older Chrysler trucks, 318, 383, 365 (?), and there was never too much of an issue with getting the coolant system filled.

I think you're again, over-thinking this. BTW, anyone buying that year truck should expect repair and maintenance to continue. The stalling of the engine is coincidental to the coolant system, not a cause from it. You may be getting some steam on the radiator or the engine if there was any coolant on those parts. Looking at the radiator, you may also have a leak in a core but that is not something to worry about now. The hoses should be tight and slightly expanded form the hot coolant. It may be that you bought a higher temp thermostat than what was originally in the van. They are not all the same. Coolant temps should reach at least 1/2 up on the gauge for engine health and best operating conditions (assuming gauge is accurate).

If you can't get the air bubble out, last resort (with stone cold engine) is to remove the thermostat standpipe and slowly fill the thermostat housing with coolant. Having vehicle facing uphill will help put the housing as the high point where air will collect.

Better than doing damage by super-heating some parts of an older engine.

And, agee, not AIR will not open a thermostat. It was designed to work on not COOLANT/WATER.

With an air bubble against the thermostat I suppose it is possible to boil the coolant before enough heat gets to the thermostat to open. This is why I recommend idling until all is flowing good.

Hrmmm, I don't think so but possible. We took it 9000 miles and drove some very long days and one would think it would have reached peak temp. Though saying that I was always impressed with it rarely running above 1/4-1/3 hot on the temp gauge.

Thinking about this, mine didnt have the little air release valve you showed me but there must be some allowance for cold coolant to get through because when I was doing the initial fill I would hold my hand on the upper hose and feel air bubbles coming up. I would wait for coolant to drop below level of upper hose (bubbles stopped) and then top up, repeated until no more bubbles.

But that doesn't help me in this situation.

Going to take it in for a check up and ask them to use their magical expensive equipment to test everything is working fine. I am in the process of selling it and don't want to new owner coming back with problems.

Learned the old 1/16" hole in the thermostat flange trick in 1972 with '51 Willys. Something to do with design of water bypass hose system or lack thereof. Just like with the choke on the F134 engine. No choke no start. Pour gas, ether, H-Bomb down carburetor...no chokee no startee.

By the way I tried many thermostats and none opened before the engine boiled. Drilling a 1/16" hole made the system heat up just as fast as anything else I have ever owned.

Ain't life grand !

Any chance the old thermostat was stuck partially open? Probably all is normal once the air bubble is chased out. Engine may have effectively been running cold for a while. Seen this plenty of times. Temperature gauge should rise steadily but may read higher than you are used to. DO NOT EVER open the cap if the hoses are stiff with pressure, let the engine cool.

I understand the best thermostats are all brass and called "balanced sleeve"

time2roll wrote:
Yes it will overflow as the air bubble expands due to rise in temperature.
All you can do is attempt to catch the overflow. When the thermostat opens the radiator will seem to go empty. Keep topping off for 5 to 10 additional minutes.

I assume you have a coolant recovery bottle. This will chase any remaining air out of the system during the first few heating and cooling cycles.

I have always thought about drilling a 1/16" or 1/8" hole in the flange but have never tried it. Can't see that it would hurt much. Could go down and ask for a premium thermostat and see if it has the release hole. Or possibly remove the thermostat during the initial fill to that level. Still need to observe the thermostat open and verify the level before you roll.

No idea why it shut off.

Did you have the old thermostat in during chem clean? Probably had the release valve. Dig it out of the trash and inspect.

Thank you sir.

Yup, it's got an overflow reservoir.

So that's what they meant when they asked if I wanted basic or premium! Last time I was given the option in a part there wasnt any difference other than "lifetime" or "1 year" warranty. The parts person didnt know what they were talking about as I queried this again and they had no answer.

But certain old one didnt have a release valve. I held them up against eachother. The garbage man has taken it to a better place now though so can't double check.